Why are we talking about Perovskite Solar?
From France to Australia, breaking efficiency records in labs around the World, Perovskite Solar is the poster child for solar research today. Efficiency data from NREL tables, which represents global lab results, shows that this technology has grown most rapidly in demonstrated conversion efficiency amongst all emerging and thin-film technologies. Given that perovskite solar can be fabricated simply by spin coating, based on the principle of depositing liquids, the technology also promises to have low manufacturing costs.
So what is Perovskite Solar?
Perovskite refers to any generic crystal structure of the type ABC3. Imagine the central ion of a cube made up of type A, the vertexes of the cube of type B and the faces of the cube having ions of type C.
A solar cell made up of a thin film of any crystal of type ABC3 is referred to as a perovskite solar cell.
In research labs Perovskite solar cells have shown the following results:
- High open circuit voltages
- High optical absorption efficiency
- Excellent charge carrier transport, i.e. less energy is lost by recombination of the charge carrier once it is excited
All these factors point towards good efficiencies and hence are incentives to carry out further research in Perovskite solar.
But why does Perovskite Solar work?
The Perovskite solar cells tested in labs are unique combinations of organic and inorganic ions. The table below shows sample combinations of ions used to create Perovskite solar cells. The organic component allows for high mobility of the charge carrier while the inorganic component ensures easy, uniform, repeatable and sustained crystal formation. With the right A, B and C combinations, the band gap and Voc can be optimized, stability maximized and degradation reduced.
|Organo||Metal||Trihalide (or trihalide)|
|Methylammonium||Lead||Iodide (or triiodide)|
|Plumbate||Chloride (or trichloride)|
Why aren’t we buying Perovskite Solar Panels yet?
There are still a few concerns with Perovskite solar cells because of which they are mostly limited to laboratories:
- Stability: Having an organic component this technology has shown potential degradation that involves water, oxygen, and the diffusion of electrode materials. Research is underway with the addition of stabilising agents.
- Use of Toxic Lead: Most stable cells in research currently uses lead, even though in small percentages. The good news is that a patent is recently been granted for a Germanium Perovskite solar cell that is deposited with Tin instead of Lead.
- Thick layer deposits: The technology currently requires that the perovskite cell layers be relatively thick )as compared to other thin film technolgies). Producing a thick layer uniformly is not quite feasibility with most large scale technologies.
I am excited to see how research in Perovskite Solar pans out. Based on a study of the existing work, one thing I can say with confidence is this this poster child of solar research cannot be ignored. Watch mono and poly-crystalline solar, you have a new competitor coming soon!